A writing utensil has been known which automatically controls the delivery of raw ink, specifically which includes an ink reservoir in its barrel and replenishes its application body (nib body) with ink contained in the ink reservoir successively with the consumption of ink in writing or coating so that writing or coating can be performed continuously. For example, Japanese Utility Model Publication No. 60-69690 describes a raw-ink delivery controlling mechanism that includes an ink absorber arranged in the ink flow path between the ink reservoir and the tip of the application body in its barrel and flows ink by means of pressure generated by ink movement in capillary (capillary osmotic pressure) which is caused in response to writing, thereby allowing continuous-writing.
In conventional delivery controlling mechanisms of applicators which contain raw ink, an ink absorber is used to absorb the ink over flowing from the raw-ink reservoir mainly to control ink's overflow so that the ink should not drip from the application body etc.
As this type of ink absorber, an ink absorber having a hollow cross section (doughnut-shaped ink absorber) has been generally used and the ink absorber is arranged in parallel or in series with the ink flow path running from the ink reservoir to the application body so that the ink absorber is in contact with the ink flow path throughout its length or at its upper portion only.
In this arrangement, it goes without saying that the length of the ink flow path from the ink reservoir to the tip of the application body is larger than the length of the ink absorber. In such a case, when intending to increase the volume/capacity of the ink absorber while meeting the requirement that an ink absorber of the same material should be installed in a barrel of a prescribed inside diameter, there is no other way but to increase the length of the ink absorber, which in turn requires the length of the ink flow path to be increased.
This gives rise to a problem of the flow of ink fed from the ink reservoir to the application body becoming slow, because it is a general physical phenomenon that the viscosity resistance of ink passing through a small-diameter ink flow path increases as the length of the ink flow path increases. And when intending to increase the diameter of the ink flow path so as to overcome the problem, an adverse effect is produced of decreasing the area in the barrel's inside/transverse section in which the ink absorber is to be installed, thereby relatively decreasing the capacity for absorbing ink, or of making it hard to form the sectional shape of the ink absorber. Thus there remains many difficulties in increasing the capacity of the ink absorber in a raw-ink applicator in which the inside diameter of its barrel is set at a prescribed thickness or in producing an applicator whose ink capacity is large. In addition, there remain other problems in applicators which use such an ink absorber, such as insufficient drip-preventive performance.
The main problems that have caused troubles and therefore having been desired to overcome are as follows.    (1) Generally an ink absorber is installed in such a manner as to be in contact with ink in the ink flow path; as a result, it absorbs of itself ink in the ink reservoir even under normal storage and it is easy to fill with ink to almost saturated state. If gas expansion takes place in the barrel under these conditions due to environmental changes and ink is pushed out from the ink reservoir, ink drips from the application body since the capability of the ink absorber to absorb the overflowing ink is insufficient.    (2) In the usage environment, since pressure or temperature changes take place repeatedly, gas in the ink reservoir repeats its contraction/expansion. Accordingly, even if the ink absorber can absorb the ink pushed out from the ink reservoir at the time of gas expansion, the absorbed ink can sometimes remain in the ink absorber, and the absorber cannot be restored to the state before absorption even at the time of gas contraction. In such a case, the same problem as (1) arises.    (3) When producing a product having a large ink capacity or a product which is filled with ink having a high vapor pressure, such as oil-based ink, the change in gas expansion in the ink reservoir is increased. In such a case, when removing the cap fitted on the barrel to close the same, for example, the gas in the barrel expands so promptly that the ink absorber cannot absorb and hold the ink, resulting in occurrence of the drip of ink.